Device for promoting and controlling aspiration



Aug. 19, 1941. H. A. WOODS DEVICE FOR PROMOTING AND CONTROLLING ASPIRATION Filed Jan. 9, 1940 FiG.2.

INVENTOR HERBERT A. Wooos BYMU-M ATTORNEY Patented Aug. 19, 1941 DEVICE FOR PROMOTING AND CONTROLLING ASPIRATIQN Herbert A. Woods, St. Louis, Mo.,' assignor to Carter Carburetor Corporation, St. Louis, a corporation of Delaware Appiication'lanuary 9, 1940, Serial No. 313,079

3 Claims.

This invention relates to devices for promoting aspiration and more particularly relates to airfoil means for varying the static pressure in a fluid stream at a point local to an aspirating nozzle.

The wide utility of a device of this character is apparent. An internal combustion engine carburetor, of the plain tube type, provides an excellent example of one use of the invention. It is well understood. by designers of internal combustion engines, that to approach maximum power output, restriction of the induction conduit must be minimized. Obviously, this means lower induction velocity and as this velocity is reduced beyond a critical point, difliculty in providing fuel by aspiration is encountered. This critical limit is closely approached in currrent engines during low speed, full volume operation,'

as occurs in automotive engine service. While a device which aids in fuel aspiration under these conditions of, operation is desirable, it is also evident that at normal engine speeds this aid may be dispensed with. Further, due to thewide speed range of automotive engines, it has been found in practice that a device capable of impedinvention in principle. The separate views being different operative positions.

Fig. 4 is a vertical section through a downdraft plain tube carburetor showing one form of my invention adapted thereto.

Referring to Figs- 1 to 3, numeral -*l indicates an airfoil element which is rotatably mounted on a shaft 2. A nozzle 3 on the left and adjacent the airfoil is indicated.

In operation, a steam of air or other fluid is caused to flow about the air foil and nozzle in a direction as indicated by the straight arrows. A normal sub-atmospheric pressure will exist in the air stream in areas not affected by the airfoil.

It will be seen, however, upon referring to Fig. 1 that the left or nozzle side of the airfoil, when inthis position is subjected to kinetic pressure f tending to straighten the airfoil. The airfoil reaction to this pressure will, obviously, set up a ing the natural increase in proportionate fuel flow at higher speeds is desirable.

It-is an object of this invention to so construe and associate an airfoil and an aspirating nozzle as to cause a localized reduction in static pressure in the vicinity of the nozzle discharge point when these elements are disposed in a fluid stream.

It is a further object of this invention to provide adevice of-.the above character in which the airfoil is movable with relation to the aspirating nozzle whereby the air stream may be deflected so as to vary the pressure in the vicinity of the discharge point of the aspirating nozzle. 7.

It is a further object of this invention to provide a device of the above character in which a device responsive to the static pressure in the air stream is provided'for positioning the movable airfoil.

It is a further object of this invention to provide a carburetor incorporating a device of the above character in which means responsive to pressure posterior to the carburetor throttle valve is provided for positioning the airfoil.

Other objects and advantages will appear in the following description and accompanying higher pressure in the vicinity of the nozzle discharge point than would exist there were the airfoil omitted or if it were in the position shown in Fig. 2. When the airfoil is rotatedyto the position shown in Fig. 3, the pressure in the vicinity of the nozzle discharge point is reduced below the subatmospheric pressure normally resulting from the velocity of the air stream, as would ocour in Fig.2. This is due to eddying and expanding in the areas immediately below the discharge tip as indicated by curved arrows.

In experiments with this device, using air stream velocities equivalent to those encountered in current carburetors during low engine speeds with a wide open throttle, manometer readings indicate as much as 50% reduction in pressure in the vicinity of the nozzle discharge tip when the airfoil is moved from the position shown in i Fig. 2 to the position shown in Fig. 3.

drawing in which like numeralsrefer to like parts.

Figs. 1, 2 and 3 diagrammatically illustrate the Referring to Fig. 4, numeral 4 generally indicates relevant structure of a downdraft carbu-,

retor of the plain tube type embodying a form of the invention. An air inlet passage 5 and a mixture conduit 6 are provided in the inlet casting and main body casting 8, respectively. The usual venturi shape 9 is provided in the body casting and an aspirating nozzle discharging into the throat of the venturi is indicated at ID. The

nozzle Ill is in communication with a constant tional ,withthis type of carburetor construction,

such as idling systems, accelerating. pumps and choking devices (not shown) is contemplated.

A throttle valve l3 mounted for rotation with a shaft l4 controls the outlet of the carburetor. The carburetor is further provided with a flange I! at its lower "end and suitable means (not shown) .for attachment to a companion flange IS on an intake manifold I1, is provided. Pivotally mounted in the mixing conduit on a shaft 2 is an airfoil element I. Means for oscillating the airfoil to the right or left of a vertical position com- Q prises a lever l8 which is rigidly attached at one end tothe shaft 2 and at its other end to a piston l9 through a link 20 and a piston rod 2|. The piston is is closely fitted within a cylinder 22. A tube 23 connects the lower end of cylinder 22 with the intake manifold H. A spring 24 within the cylinder 22 normally urges the piston upward and consequently positions the airfoil as shown in full lines. A stop 25 rigidly affixed to the Diston rod 2| limits the'upward travel of the piston and a projection 26 abuts the lower end of the cylinder and thereby limits the downward travel of the piston when the airfoil hasbeen moved to the position indicated by dotted lines.

The operation of the device shown in Fig.4

is as follows:

Assuming an-e'ngine to which the carburetor is attached to be operating near its minimum operative speed under full load with the throttle valve .wide open as indicated. At'this time very little vacuum exists in the intake manifold andthe piston 19 is, therefore, urged to its upward limit by the spring 24 and-the airfoil l is moved to the position indicated in full line. Under these conditions of operation, static pressure in the vicinity. of the nozzle-discharge point would ap moved towarda vertical or normal position by the piston, which responds to the increase in wherein it functions to provide a local area of increased pressure at the nozzle tip thus impeding aspiration.

I am aware that various adaptations and modifications of the foregoing disclosure are obvious to those skilled and therefore desire the sole use of all modifications within the scope of the appended claims. y

. I claim:

1. In a carburetor, a mixture conduit having a portion thereof formed as a venturi tube, a fuel nozzle discharging into the throat of said venturi at one side thereof, an airfoil pivotally mounted in said venturi comprising a plate of comparatively thick section at the throat of said venturi and tapering to a thin section downstream thereof and being transversely pivoted substantially at the throat of said venturi so as to form.

with the venturi tube a variably diverging outlet for the mixtureon said side of the venturi, and

means subjected. to and movable by the static point of thickest section, a fuel nozzle discharg-' ing into said conduit at one side of said airfoil and inthezone of lowest static pressure adjacent the most constricted point, and means subjected to and movable by the static pressure in said conduit for shifting said airfoil so as tof vary the angle of downstream divergence from the most constricted point on the nozzle side of said airfoil.

manifold vacuum resulting from "increasedspeed. As the engine speed continues to increase and approaches its maximum the piston is drawn downward to its limit and the airfoil is moved to the position shown by dotted lines,

3. In a carburetor, a mixture conduit, an air-"- foil pivoted in said conduit comprising a plate of comparatively thick section at its upstream edge and tapering to a thinner section downstream therefrom and being pivoted at its thickest most constricting point, a fuel nozzle discharging into said conduit on one side of said airfoil and in the zone of lowest static pressure adjacent the most constricted point, resilient means for urging said airfoil in a direction. away from said nozzle so as to increase the angle of divergence downstream therefrom between the wall of the conduit and the airfoil, and means communicating with said conduit 'and responsive to decreasing pressure therein for moving said airfoil in an opposite direction. HERBERT A. WOODS. 

